The main objective of this ongoing program is the systematic investigation of the anatomy and physiology of, and effects of pathological lesions on, the vestibulo-ocular system. The studies are conducted on cats and rabbits with normal or experimentally modified vestibulo-oculomotor systems. These studies are expected to provide quantitative information about vestibulo-ocular reflex responses, particularly those of nystagmus. This includes: (1) detailed measurements of the nystagmus parameters, (2) estimates of the contribution of the individual labyrinthine receptors--semicircular canals and otoliths-- to production of reflexes in the form of input-output functions, (3) data on the participation of the individual extrinsic nerve cells and muscles of the eye in each nystagmus beat, and (4) the development of models for the prediction of changes in vestibular responses due to abnormalities in the contributing elements of the vestibular reflex arc. A continued effort is being made toward the development of techniques, including the utilization of the computer, for the control of stimuli using deterministic and stochastic signals to the receptor organs, for the characterization of the parameters of the eye movements, and for parametric determination of the coefficients of transfer function which describe the behavior of the vestibulo-oculomotor system.